Two New Corneal Diseases Characterized by Recurrent Erosions

Sammanfattning: Recurrent corneal erosions are a common complication of superficial corneal wounds. They most commonly arise following a trauma, in association with various corneal dystrophies, or are idiopathic.The main aim of this thesis was to investigate two hereditary corneal diseases with recurrent erosions in order to find out if they had been described before, and more specifically to describe the clinical picture and the morphological changes, differentiate them from other known autosomal dominant corneal dystrophies with a clinical resemblance, and to exclude genetic linkage to known corneal dystrophies with autosomal-dominant inheritance and a clinical resemblance.The thesis is based on two families of subjects belonging to different phenotypes. The subjects from Småland (Dystrophia Smolandiensis) belonged to a six-generation family, which included 171 individuals of whom 44 were affected individuals, and the family from Hälsingland (Dystrophia Helsinglandica) included sevengenerations of 342 individuals, of whom 84 were affected. The individuals in both families were investigated by collection of medical history through medical records and questionnaires assessing different aspects of the diseases, pedigree analysis, and from clinical examination. Haplotype analysis was used to exclude genetic linkage of both diseases to known autosomal-dominant corneal dystrophies with a clinical resemblance. The morphological changes in Dystrophia Smolandiensis were investigated by examining affected individuals with in-vivo confocal microscopy and/or slit-lamp biomicroscopy, and examining corneal tissue samples using histopathology and immunohistochemistry. In Dystrophia Helsinglandica, the morphological changes were described using in-vivo confocal microscopy and/or slit-lamp biomicroscopy, but also using videokeratography and corneal sensitivity measurement.The main results were the findings of two new corneal disorders with autosomal dominant inheritance, characterized by recurrent corneal erosions.In Dystrophia Smolandiensis the symptoms often started within the first year of life. The number of recurrences per year was highest from the onset and for about 30-40 years, and the duration of recurrence could stretch up to 21 days. The frequency of recurrences was variable in the disease from continuous symptoms to once a year and tended to decrease later in life. The risk of having recurrences did not disappear completely with age. Typical precipitating factors of recurrence were draught and a common cold. About two thirds of the affected individuals responded well to oral vitamin B treatment, but no other therapy has so far been successful. In Dystrophia Smolandiensis development of corneal opacifications or secondary scarring of varying type and degree was seen in about half of the subjects. Opacifications were first noted at the age of about 7 years, but usually first seen at the age of 20-40 years. Corneal grafting was performed in nine individuals, and recurrences were seen in all grafts. The corneal buttons showed epithelial hyperplasia, partial or total loss of Bowman’s layer, and subepithelial fibrosis in the light microscope. The deeper stroma, Descement’s membrane, and endothelium were normal. Confocal microscopy confirmed loss of Bowman’s layer and revealed that the corneal nerves either were normal in their sub-basal plexa or showed signs of regeneration. None of the morphological findings were specific. We believe that the opacifications are reactive corneal changes to repeated erosive events.The onset in Dystrophia Helsinglandica was usually at the age of 4-7 years and late-developing subepithelial fibrosis not significantly affecting visual acuity was seen in all affected individuals over the age of 37 years. The number of recurrences per year was highest from the onset and for about 20-30 years, and the duration of recurrence was usually up to about a week. The frequency of recurrences tended to decrease in the disease with increasing age, but did not cease completely. The precipitating factor of recurrence was typically a minor trauma. No therapy has so far been successful in the family. The corneal changes of affected individuals were classified into different stages from a nearly normal cornea to progressive fairly discrete subepithelial fibrosis of the central cornea. Discrete localized Subepithelial fibrosis in the periphery or mid-periphery (stage I) was the sole finding in 12% of the individuals. A more widespread subepithelial fibrosis, mainly in the mid-periphery, was found in 31% of the individuals (stage II). In stage III, the subepithelial fibrosis engaged the central cornea but did not affect the vision to a significant degree. In late phases of stage III small jellylike corneal irregularities could be seen. We believe that the opacifications are reactive changes to repeated erosive events.In conclusion this thesis describes two new corneal disorders – Dystrophia Smolandiensis and Dystrophia Helsinglandica.